1. Field of the Invention
The present invention is directed to a torsional vibration damping arrangement, preferably for the drivetrain of a vehicle.
2. Detailed Description of the Prior Art
Torque-transmitting torsional vibration dampers, vibration absorbers, and torsional vibration damping arrangements are often installed for enhancement of driving comfort and for suppression of vibrations in the drivetrain. Generally speaking, vibration absorbers, or tuned mass dampers, of this type are additional masses coupled with the drive system or torsional vibration damper by a spring system. A vibration absorber operates in such a way, for example, that a vibration system comprising a main mass and an additional mass is so tuned with respect to its natural frequency that at a certain excitation frequency the additional mass, referred to hereinafter as absorber weight or deflection mass, carries out a forced vibration, while the main mass remains at rest so that vibration frequencies can be efficiently suppressed.
In order to achieve the suppression of vibrations over a larger range of speed, speed-adaptive vibration absorbers, or tuned mass dampers, are used whose natural frequency or resonant frequency changes as a function of speed, for example, proportional to the speed. Thus by vibration absorber and torsional vibration damping arrangement is meant herein a device or mechanism or arrangement of components by which no torque is transmitted and which is capable of removing energy from the drivetrain at a determined, possibly variable, vibration frequency in order to suppress torsional vibrations occurring at this frequency.
To achieve a suppression of vibrations depending on speed in a torsional vibration damping arrangement of the type mentioned above, is it suggested in German Patent Application 10 2010 053 542 A1 that a flywheel which is rotatable around an axis of rotation is connected via a pendulum arm to a pendulum mass which is movable in circumferential direction relative to the flywheel, which pendulum arm extends substantially radially and can deform elastically. The pendulum arm can oscillate elastically around an oscillating point in circumferential direction, and the position of the oscillating point can be varied in radial direction. Through the oscillating point which can vary in radial direction, an imaginary pendulum length acting at the pendulum mass can be changed so that the pendulum mass can oscillate at a variable frequency and can accordingly damp different frequencies. It is further suggested that the oscillating point be displaced radially outward as a function of rotational speed in order to adapt the damping characteristics to the instantaneous rotational speed of the drivetrain.
While this solution may ensure a continuous tracking of the frequencies that can be efficiently damped, it has the disadvantage that comparatively large changes in the excitation frequency at a certain engine speed cannot be taken into account. In particular, torsional vibration damping arrangements of this type can only be configured for a damping order corresponding, e.g., in a combustion engine, to a predetermined cylinder count in a predetermined combustion stroke. This is because the rotational irregularities of internal combustion engines are predominantly generated by the cycled combustion of conventional reciprocating piston engines. It is not possible with the torsional vibration damper known in the art to tune the torsional vibration damping arrangement, e.g., to the fundamental frequency of the rotational irregularity in a first speed range of the engine and, e.g., to the first harmonic excitation of the fundamental frequency in a second speed range.